Median barriers are provided along highways for high-speed vehicle travel to prevent a vehicle in one lane, out of control, from jumping into the oppositely traveled lane across a median strip and endangering the drivers, passengers, etc. of both the wayward vehicle and oncoming traffic.
It is already known in connection with vehicle guard rails to provide rail structures along a traffic lane which are positioned substantially on the level of the center of gravity of the vehicle to be intercepted and designed to absorb impact energy with a medium of rebounding. The term "rebounding" is used herein to designate the deflection of a vehicle which leaves its lane back into the traffic flow in its original direction. In the last mentioned applications, I have described systems whereby the guard rail is cushioned or formed so as to prevent or limit the breakage of the rail structure or its distortion in a manner leading to the production of sharp edges which might endanger the vehicle passengers. This structure deflects laterally over long distances by the breakaway of its supporting posts so as to allow the rail to form a sling-type loop along which the vehicle slides to prevent rebounding.
Earlier barriers provided a more or less rigid wall which crushed, broke and presented sharp edges or corners which tore the vehicle and endangered its passengers.
To provide assurance that high-speed vehicles would not cross the median barrier, prior efforts at developing effective vehicle controls for this purpose have concentrated upon rigid and massive structures disposed along the median strip.
When, however, the median barrier is provided at the level of the center of gravity for most normal passenger vehicles, it is too low for trucks, buses and similar large vehicles which tend to leap the barrier.
On the other hand, when a rigid rail structure is provided at the level of the center of gravity sufficient to catch most large vehicles, it is well above the major part of the body of a passenger vehicle and is dangerous to the passenger compartment of a passenger vehicle when the latter impacts against the median barrier.
All efforts heretofore to provide a median barrier for use on highways traveled by trucks and like large vehicles in addition to passenger vehicles have hitherto been compromises both as to massive, height and the like considering that trucks and passenger vehicles may differ in weight between 5 and 20-fold while the height of the center of gravity may be twice or three times greater in a truck than in a passenger vehicle.
It will immediately be appreciated that a median rail which is sufficient in mass or rigidity to halt a massive truck will result in complete demolition of a passenger vehicle impacting thereagainst at high speed and will generally be positioned at a level detrimental to the safety of the passengers.